Solvent-Free Synthesis of MgO-Modified Biochars for Phosphorus Removal from Wastewater

Abstract

Adsorption is an efficient technology for removing phosphorus from wastewater to control eutrophication. In this work, MgO-modified biochars were synthesized by a solvent-free ball milling method and used to remove phosphorus. The MgO-modified biochars had specific surface areas 20.50–212.65 m2 g−1 and pore volume 0.024–0.567 cm3 g−1. The as-prepared 2MgO/BC-450-0.5 had phosphorus adsorption capacities of 171.54 mg g−1 at 25 °C and could remove 100% of phosphorus from livestock wastewater containing 39.51 mg L−1 phosphorus. The kinetic and isotherms studied show that the pseudo-second-order model (R2 = 0.999) and Langmuir models (R2 = 0.974) could describe the adoption process well.. The thermodynamic analysis indicated that the adsorption of phosphorus on the MgO-modified biochars adsorbent was spontaneous and endothermic. The effect of pH, FTIR spectra and XPS spectra studies indicated that the phosphorus adsorption includes a protonation process, electrostatic attraction and precipitation process. This study provides a new strategy for biochar modification via a facile mechanochemical method.

Recyclable Magnesium-Modified Biochar Beads for Efficient Removal of Phosphate from Wastewater

“…As shown in Figure 7 , the equilibrium adsorption capacity of the adsorbent on PO 4 -P was 72.9% of the original capacity after five cycles. The declined performance should be ascribed to the loss of adsorption sites with strongly trapped adsorbates [ 14 ]. However, the decline rate of the capacity of the adsorbent was much lower than that of biochar adsorbents reported in the literature [ 35 ], indicating the adsorbent promoted in this work is favorable for recycling.…”

“…Therefore, the capacity of the adsorbents can be increased in two ways for phosphate adsorption: (a) the introduced metal oxides are expected to increase the electrostatic attraction and precipitation with the adsorbates, and (b) the reduced particle size and increased surface activities are believed to enhance the active sites for adsorption. Till now, various metal oxides, such as CaO [ 13 ] and MgO [ 14 ], have been successfully introduced into biochar through ball milling. In particular, Xu et al [ 14 ] recently prepared MgO-modified biochar by pyrolyzing the co-milled composites of biomass and Mg(CH 3 COO) 2 ·4H 2 O, which greatly avoids extra energy loss as the biochar and the metal oxides can be formed at the same time.…”

“…Till now, various metal oxides, such as CaO [ 13 ] and MgO [ 14 ], have been successfully introduced into biochar through ball milling. In particular, Xu et al [ 14 ] recently prepared MgO-modified biochar by pyrolyzing the co-milled composites of biomass and Mg(CH 3 COO) 2 ·4H 2 O, which greatly avoids extra energy loss as the biochar and the metal oxides can be formed at the same time. However, these milled composites usually exhibit good dispersion in water with their nano sizes, thus may result in secondary contamination without the property for easy separation and collection [ 15 ].…”

High Purity Struvite Recovery from Hydrothermally-Treated Sludge Supernatant Using Magnetic Zirconia Adsorbent

“…As presented in Table 3 , r 2 values for the pseudo-second-order model were higher than those for the pseudo-first-order model, indicating that the adsorption mechanism of MZ for phosphate is chemisorption [ 36 ].…”

“…After adsorption, MZ with adsorbed phosphate was magnetically separated and subjected to desorption treatment. The effect of two desorption agents, NaOH and NaCl, and their combinations on the desorption were investigated [ 36 , 40 , 41 ], and the results are presented in Figure 5 . The desorption effect of NaCl was poor, with desorption rates between 6–8% regardless of the NaCl concentration.…”